1. Field of the Invention
The present invention relates to an audio processing device that performs audio signal processing to a digital audio signal.
2. Description of the Related Art
As an audio processing device that performs audio signal processing such as D/A conversion and amplification to a digital audio signal, there is an AV receiver. The AV receiver that is described in JP 2013-046265 A performs audio signal processing to the digital audio signal and outputs an analog audio signal to main speakers that are located in a main room (main output route (first output route)). The AV receiver that is described in JP 2013-046265A performs audio signal processing to the digital audio signal and outputs the analog audio signal to Zone2 speakers (sub speakers) that are located in a Zone2 room (sub room) (Zone2 output route (second output route)).
FIG. 5 is a block diagram illustrating a configuration of a conventional AV receiver. For example, an AV receiver 101 can perform audio signal processing to a 7.1 channels digital audio signal. As illustrated in FIG. 5, the AV receiver 101 includes a DSP 105, a Zone2 reproduction device 106, and DACs 107 to 111. The DSP 105 is a device that reproduces the digital audio signal. The DSP 105 is a device for reproducing an audio signal that is output to the main speakers. The Zone2 reproduction device 106 is a device that reproduces the digital audio signal. The Zone2 reproduction device 106 is a device for reproducing an audio signal that is output to the Zone2 speakers. Each of the DACs 107 to 110 D/A-converts the digital audio signal that is output from the DSP 105 into the analog audio signal. Each of the DACs 107 to 110 can D/A-convert DSD (Direct Stream Digital) data and PCM (Pulse Code Module) data. Further, each of the DACs 107 to 110 is a 2 channels DAC.
A front left digital audio signal and a front right digital audio signal are input to the DAC 107. The DAC 107 D/A-converts the front left digital audio signal and the front right digital audio signal into a front left analog audio signal and a front right analog audio signal and outputs the front left analog audio signal and the front right analog audio signal to a front left analog output terminal and a front right analog output terminal. A center digital audio signal and a subwoofer digital audio signal are input to the DAC 108. The DAC 108 D/A-converts the center digital audio signal and the subwoofer digital audio signal into a center analog audio signal and a subwoofer analog audio signal and outputs the center analog audio signal and the subwoofer analog audio signal to a center analog output terminal and a subwoofer analog output terminal. A surround left digital audio signal and a surround right digital audio signal are input to the DAC 109. The DAC 109 D/A-converts the surround left digital audio signal and the surround right digital audio signal into a surround left analog audio signal and a surround right analog audio signal and outputs the surround left analog audio signal and the surround right analog audio signal to a surround left analog output terminal and a surround right analog output terminal. A Surround back left digital audio signal and a surround back right digital audio signal are input to the DAC 110. The DAC 110 D/A-converts the surround back left digital audio signal and the surround back right digital audio signal into a surround back left analog audio signal and a surround back right analog audio signal and outputs the surround back left analog audio signal and the surround back right analog audio signal to a surround back left analog output terminal and a surround back right analog output terminal.
The DAC 111 D/A-converts the digital audio signal that is output from the Zone2 reproduction device 106 into the analog audio signal. The DAC 111 can D/A-convert the PCM data but cannot D/A-convert the DSD data. Further, the DAC 111 is a 2 channels DAC. A Zone2 left digital audio signal and a Zone2 right digital audio signal are input to the DAC 111. The DAC 111 D/A-converts the Zone2 left digital audio signal and the Zone2 right digital audio signal into a Zone2 left analog audio signal and a Zone2 right analog audio signal and outputs the Zone2 left analog audio signal and the Zone2 right analog audio signal to a Zone2 left analog output terminal and a Zone2 right analog output terminal.
A front left speaker and a front right speaker are respectively connected to the front left analog output terminal and the front right analog output terminal. A center speaker and a subwoofer speaker are respectively connected to the center analog output terminal and the subwoofer output terminal. A surround left speaker and a surround right speaker are respectively connected to the surround left analog output terminal and the surround right analog output terminal. A surround back left speaker and a surround back right speaker are respectively connected to the surround back left analog output terminal and the surround back right analog output terminal. The main speakers are configured by the front left speaker, the front right speaker, the center speaker, the subwoofer speaker, the surround left speaker, the surround right speaker, the surroundback left speaker, and the surround back right speaker. The main speakers reproduce an audio according to a 7.1 channels analog audio signal that is output from the DACs 107 to 110.
A front left speaker and a front right speaker are respectively connected to the Zone2 left analog output terminal and the Zones2 right analog output terminal. The Zone2 speakers are configured by the frond left speaker and the front right speaker. The Zone2 speakers reproduce an audio according to a 2 channels analog audio signal that is output from the DAC 111.
In the above mentioned conventional AV receiver 101, a cheap device that cannot D/A-convert the DSD data in which data quantity is large is used as the DAC 111 for Zone2 to reduce product unit price. For this reason, there is a problem that the DSD data cannot be reproduced and output to the Zone2 room.